1. Field of the Invention
This invention relates to a high-voltage transformer such as an ignition coil for internal combustion engines, and more particularly, to a connecting arrangement for connecting a coil with an output terminal. This invention is also concerned with a method for making a high-voltage transformer.
2. Description of the Prior Art
FIG. 1 is a plan view showing a conventional high-voltage transformer for internal combustion engines, and FIG. 2 is a cross sectional view taken along line II--II of FIG. 1. In these figures, the high-voltage transformer 1 in the form of an ignition coil comprises a generally cylindrical coil case 2 formed of a synthetic resin, a primary coil 3 in the coil case 2, a secondary coil 4 disposed in the coil case 2 so as to surround the primary coil 3, a cylindrical sleeve 5 disposed in and fixedly mounted on the coil case 2 substantially at the center thereof for receiving a rotary shaft 8 of a distributor (not shown), and an iron core 6 disposed in the coil case 2 around the sleeve 5 so as to surround the primary coil 3 and the secondary coil 4.
The iron core 6 comprises an annular inner or central leg portion 601 disposed around the cylindrical sleeve 5 and radially inside the primary coil 3, four planar outer leg portions 602 disposed radially outside the secondary coil 4, a pair of first (or lower) and second (or upper) cross-shaped arm portions 603 and 604 interconnecting the inner and outer leg portions 601 and 602 for forming a closed magnetic path which passes through the primary and secondary coils 3, 4 when these coils are energized.
A resin 7 is filled into the coil case 2 and impregnated into the spaces between the coils 3, 4 and the iron core 6 for electrically insulating the coils 3, 4 and the iron core 6 from each other as well as for firmly securing or bonding them to the coil case 2. In this case, the lower arm portion 603 of the iron core 6 is molded integrally with or firmly connected by other appropriate fastening or bonding means with the coil case 2, and it is exposed to the outside of the coil case 2 for dissipating heat which is generated during molding of the coil case 2 or the like.
A high-voltage terminal 9 is integrally mounted as by molding on the coil case 2 on its one side for taking out the high-voltage output of the secondary coil 4. The terminal 9 is electrically connected at one end with a lead wire or output end 4a of the secondary coil 4 and at other end with an external electrical device such as, for example, a central electrode of a distributor cap (not shown), which is attached to the center of a distributor rotor (not shown) mounted on the rotary shaft 8 for integral rotation therewith.
With the conventional high-voltage transformer 1 as constructed above, the high-voltage terminal 9 is integrally molded with the coil case 2 at the time when the coil case 2 is molded from a synthetic resin. Assembly of the entire transformer 1 is effected as follows. First, the iron core 6, the primary coil 3 and the secondary coil 4 are disposed in positions in the coil case 2. In this state, the output end or lead wire 4a of the secondary coil 4 is soldered to the high-voltage terminal 9. Thereafter, a molten resin 7 is filled into the coil case 2, impregnated inbetween the above members in the coil case 2, and solidified to firmly install or secure them to the coil case 2.
In the above assembly processes of the conventional transformer 1, however, the terminal 9 is firmly connected as by molding with the coil case 2 before the resin 7 is filled into the coil case 2. Accordingly, one must connect or solder the output end or lead wire 4a of the secondary coil 4 to the high-voltage terminal 9, which is fixed to the coil case 2 and can not be moved freely, at a location within the coil case 2 which has a relatively narrow working space. In fact, it is very difficult and inefficient to carry out such connection or soldering by passing the secondary coil lead wire 4a through a small aperture which is formed at one end of the terminal 9 even if the secondary coil lead wire 4a is made very close to the terminal lead wire 9a. Moreover, there arises another problem in that it is difficult to prevent the secondary coil lead wire 4a from sagging so as to ensure good and reliable soldering.